The present invention relates to modifying image data representing a moving image by a sequence of image frames each containing an array of pixels.
Procedures for modifying image data representing a moving image by a sequence of image frames each containing an array of pixels are known. It is known to identify a distinctive portion of an image, perceived by the eye as representing a distinctive component or item within the image frame. A tracking operation is then performed on a frame-by-frame basis in order to follow movement of the item for the duration of a video clip. This results in displacement vectors being generated representing movement of the item on a frame-by-frame basis. This information is stored and may then be used to define how a mask or a matte should move on a frame-by-frame basis in order to perform a compositing process.
A problem with known tracking procedures of this type is that they are often directed towards performing a particular operation in a procedural and non-interactive way. The present inventors have realised that item movement within a scene, over a video clip, is often interactive and that movement characteristics of one item, which may be tracked, will often have temporal significance with reference to other movement occurring within the clip. Thus, there has been a realisation to the effect that tracking data could be used for more creative purposes if the tracking procedures could be carried out within a more interactive environment.
According to a first aspect of the present invention, there is provided image data processing apparatus configured to process image data representing a moving image by a sequence of image frames, wherein each of said image frames contains an array of pixels, including identifying means configured to identify a distinctive characteristic of an image frame defined by pixel transitions; generating means configured to generate a tracking parameter in response to tracking the position of said distinctive characteristics; controlling means configured to control an object in response to said tracking parameter; and display means configured to display an output image in response to the application of said controlled object upon an image frame.
In a preferred embodiment, the identifying means is configured to identify a plurality of distinctive characteristics, said generating means is configured to generate a first tracking parameter in response to tracking the position of a first distinctive characteristic, and configured to generate a second tracking parameter in response to tracking the position of a second distinctive characteristic and to generate a combined tracking parameter by combining the first tracking parameter and a second tracking parameter, wherein the controlling means is configured to control the object in response to the combined tracking parameter.
According to a second aspect of the present invention, there is provided a method of modifying image data representing a moving image by a sequence of image frames each containing an array of pixels, including the steps of: identifying a distinctive characteristic of an image frame defined by pixel transitions; and modifying image data in response to a plurality of process iterations, wherein each of said process iterations comprises the step of generating a tracking parameter in response to tracking the position of said distinctive characteristic, controlling an object in response to said tracking parameter, and displaying an output image in response to the application of said controlled object upon an image frame.